The present invention relates generally to filtering systems and in particular to a filtering apparatus that includes a replaceable filter element.
Filters are used in many applications to remove impurities from a fluid. In the case of water treatment, filters are often employed to selectively remove minerals, chemicals, and other materials. Some of these filters, such as carbon filters which are used to improve the taste and odor of water, gradually become exhausted during use. In particular, the activated carbon housed within the filter eventually becomes saturated and can no longer remove the intended impurities. If the filter is not replaced, the water quality degrades. With many, if not most, of these filters, the user does not recognize the need for replacement until the water quality suffers substantially.
U.S. Pat. No. 4,698,164 to Ellis discloses and claims a filtering apparatus which automatically terminates the flow of water through the filter after a predetermined quantity of water has passed through the filter. By terminating the flow of water automatically, the filtering apparatus prevents the user from consuming water after the water quality has degraded beyond a preset limit, possibly before any noticeable change in taste or odor. The filtering apparatus disclosed in U.S. Pat. No. 4,698,164 contains several relatively expensive components specific to the shutoff feature within the replaceable cartridge. When the cartridge is discarded, these components are lost, increasing the cost of the filter cartridge. The filtering apparatus of the U.S. Pat. No. 4,698,164 terminates the flow of water after a predetermined amount of water has flowed through the filter, but does not give the user an indication of how much life is left in the filter. The filter may therefore shut off flow without warning, causing inconvenience. In addition, remaining pressure build up in the monitoring head after the water is shut off to replace the filter cartridge often made removal of the cartridge difficult. A final drawback to the filtering apparatus of the U.S. Pat. No. 4,698,164 is that is experiences a relatively high pressure drop. Although filters constructed in accordance with the ""164 patent performed well and have enjoyed commercial success, it is desirable to enhance its functionality while reducing its manufacturing cost.
The present invention provides a new and improved filtering apparatus that monitors the water flow through a filter element and automatically terminates the flow of water after a predetermined quantity of water has passed through the filter.
The disclosure of the invention is illustrated in connection with water filtered through a carbon filter. However, it should be understood that the invention is adaptable to a wide variety of fluids and filters and should not be limited to water filtered through a carbon filter.
According to the preferred and illustrated embodiment, the filtering apparatus and system comprises a fluid monitoring head and a replaceable filter element. The monitoring head includes a fluid flow sensing mechanism for measuring the quantity of fluid passed through a replaceable filter element and a flow shutoff mechanism releasably connected to a shutoff activating device located in the filter element when the filter is attached to the fluid monitoring head. When the filter is mounted to the head, the flow shutoff mechanism forming part of the fluid monitoring head automatically couples to the shutoff activating device located within the filter element and is reset to an initial position.
In accordance with the invention, the shutoff mechanism includes a shutoff valve element which is moved when the shutoff activating device activates the flow shutoff mechanism to close off the flow path through the fluid monitoring head when a predetermined quantity of water has passed through the filter as measured by the fluid monitoring head. Since, in the preferred embodiment, the filter is intended to be a disposable item, the unit is sealed and access to the shutoff activating device is prevented; consequently the filter must be replaced to reestablish fluid flow through the system.
The preferred fluid sensing mechanism comprises a turbine disposed in the fluid flow path that is operatively connected to a reduction gear train. The gear train in turn is connected to a drive member forming part of the monitoring head which couples with a driven member also forming part of the monitoring head.
In the preferred and illustrated embodiment, the flow through the filter is not reduced as the time for replacement nears. The valve element remains substantially out of the flow path until released by the shutoff mechanism. This feature is achieved in the preferred embodiment, by a driven member that comprises a rotatable stem including structure couplable with the drive member. The rotatable stem (forming part of the fluid monitoring head) is moveable within a valve chamber and includes a tapered end for engaging the shutoff activating device located within the filter element and a life indicating end viewable to the user. The valve element comprises a piston assembly disposed on the stem between the tapered end and the life indicating end. The piston assembly includes an upper portion for engaging a spring disposed around the life indicating end of the stem which has a biasing force tending to move the stem and its piston toward the filter element. A lower portion of the piston is configured to mate with an opening in the fluid monitoring head which is part of the flow path such that when the piston is seated within the opening, fluid cannot flow out of the monitoring head.
The shutoff activating device comprises a pin having a threaded segment threadably received in threaded cavity in the filter element and having a shutoff mechanism engaging end. Relative to the filter element, the shutoff activating pin can move between two positions, an initial position at installation and a valve release position in which the threaded segment has moved through the threaded cavity and is no longer retained therein. Due to their interaction, the position of the activating pin within the threaded cavity controls the height of the stem within the valve chamber. When the pin is at its initial position, the stem is held at a position such that the life indicating end indicates that there is full life available and the piston is at its furthest location from its mating opening in the monitoring head.
When the filter is installed on the monitoring head, the tapered end of the rotatable stem engages the shutoff mechanism engaging end of the shutoff activating pin. The stem is pushed against the biasing force of the spring by the activating pin so that the life indicating pin shows full life and the lower portion of the piston is clear of the opening in the fluid monitoring head. As fluid flows through the monitoring head the turbine rotates. The rotation of the turbine drives the gear train causing the rotatable stem of the shutoff mechanism to rotate. As the stem rotates, the tapered end of the stem interacts with the shutoff engaging end of the shutoff activating pin to thread it in a direction away from the initial position toward the filter element and the valve release position. The stem remains engaged with the activating pin by virtue of the biasing force of the spring. In addition to the biasing force of the spring, a resultant downward force is exerted on the piston by virtue of ambient water pressure acting on a larger area above the piston than below the piston. When the shutoff activating pin reaches the valve release position it falls clear of the threaded cavity to allow the rotatable stem to be moved by the spring to seat the lower end of the piston in the opening in the fluid monitoring head to block the flow of fluid out of the monitoring head.
In accordance with a feature of the invention, the coupling between the monitoring head and the replaceable filter is provided by a thread type structure. The replaceable filter is preferably a molded cartridge supported in a housing which includes molded, internal threads at one end. The monitoring head includes a depending flange defining external threads adapted to receive the threads formed on the housing. With the disclosed construction, replacement of the filter is accomplished quite readily.
According to another feature of the invention, the shutoff mechanism engaging end of the shutoff activating pin comprises a unidirectional configuration such that the pin may only be turned by the tapered end of the stem or other device such as a standard screw driver in a direction which moves the pin within the threaded cavity away from the monitoring head. This feature prevents the user from counter-rotating and/or resetting the pin and continuing to use the filter element after it has exceeded its optimum filtering life. According to another feature the invention, a pressure relief valve is provided to prevent pressure build up in the monitoring head from hindering cartridge removal for replacement.
Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description made in connection with the accompanying drawings.